Personally I move any contrib that installs itself into /opt, into an ibay, it's better for various reasons.
Opinions may vary but it does not really matter where a contrib installs itself to, but there is certainly no compelling technical reason to continue installing contribs (particularly web apps) to /opt on SME server.
We should aim to stick with SME server standards & install contribs to ibays.
You are a power user, so you can do what you want
I disagree with the idea to move files of a rpm to ibays, I do not know what it can happen if you do a backup and a restoration to another server, you might have some issues, but you have the skill to solve them, so no problem for me.
A contrib is done to users who don't have the skill to trade with a webapp application, if you have the level of knowledge of doing a mysql db and installing all php files (yes it is easy) I would agree that the good place is the ibay because the server can trade with all the backup process. However backup are in the hand of sysadmin, and when you install a wordpress or any other webapp from epel, they don't provide backup for you, it is your job.
In french we have an expression 'ceinture et bretelles' (belt and braces) so you should have two ways of different backup it is most sure.
From my experience, I would follow the fedora behaviour and install all files in /usr/share.